:: a -> Maybe a -> a

The fromMaybe function takes a default value and and Maybe value. If the Maybe is Nothing, it returns the default values; otherwise, it returns the value contained in the Maybe.

Examples

Basic usage:
>>> fromMaybe "" (Just "Hello, World!")
"Hello, World!"
>>> fromMaybe "" Nothing
""
Read an integer from a string using readMaybe. If we fail to parse an integer, we want to return 0 by default:
>>> import Text.Read ( readMaybe )

>>> fromMaybe 0 (readMaybe "5")
5

>>> fromMaybe 0 (readMaybe "")
0
The fromMaybe function takes a default value and and Maybe value. If the Maybe is Nothing, it returns the default values; otherwise, it returns the value contained in the Maybe.

Examples

Basic usage:
>>> fromMaybe "" (Just "Hello, World!")
"Hello, World!"
>>> fromMaybe "" Nothing
""
Read an integer from a string using readMaybe. If we fail to parse an integer, we want to return 0 by default:
>>> import Text.Read ( readMaybe )

>>> fromMaybe 0 (readMaybe "5")
5

>>> fromMaybe 0 (readMaybe "")
0
An alternative name for fromMaybe, to fit the naming scheme of this package. Generally using fromMaybe directly would be considered better style.
Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.
Left bracket of the conditional choice operator. This is equivalent to fromMaybe
Unicode rebinding of <|.
The fromMaybe function takes a default value and and Maybe value. If the Maybe is Nothing, it returns the default values; otherwise, it returns the value contained in the Maybe.

Examples

Basic usage:
>>> fromMaybe "" (Just "Hello, World!")
"Hello, World!"
>>> fromMaybe "" Nothing
""
Read an integer from a string using readMaybe. If we fail to parse an integer, we want to return 0 by default:
>>> import Text.Read ( readMaybe )

>>> fromMaybe 0 (readMaybe "5")
5

>>> fromMaybe 0 (readMaybe "")
0
Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.
An alternative name for fromMaybe, to fit the naming scheme of this package. Generally using fromMaybe directly would be considered better style.
asProxyTypeOf is a type-restricted version of const. It is usually used as an infix operator, and its typing forces its first argument (which is usually overloaded) to have the same type as the tag of the second.
>>> import Data.Word

>>> :type asProxyTypeOf 123 (Proxy :: Proxy Word8)
asProxyTypeOf 123 (Proxy :: Proxy Word8) :: Word8
Note the lower-case proxy in the definition. This allows any type constructor with just one argument to be passed to the function, for example we could also write
>>> import Data.Word

>>> :type asProxyTypeOf 123 (Just (undefined :: Word8))
asProxyTypeOf 123 (Just (undefined :: Word8)) :: Word8
asProxyTypeOf is a type-restricted version of const. It is usually used as an infix operator, and its typing forces its first argument (which is usually overloaded) to have the same type as the tag of the second.
>>> import Data.Word

>>> :type asProxyTypeOf 123 (Proxy :: Proxy Word8)
asProxyTypeOf 123 (Proxy :: Proxy Word8) :: Word8
Note the lower-case proxy in the definition. This allows any type constructor with just one argument to be passed to the function, for example we could also write
>>> import Data.Word

>>> :type asProxyTypeOf 123 (Just (undefined :: Word8))
asProxyTypeOf 123 (Just (undefined :: Word8)) :: Word8
Hint the type system about the type.
An infix form of fromMaybe with arguments flipped.
Similar to fromMaybe but with flipped arguments.
>>> readMaybe "True" ?: False
True
>>> readMaybe "Tru" ?: False
False
Flipped version of fromMaybe, useful for chaining.
A fliped version of fromMaybe.
Set either an institute or an organization for the document. It does not work for a document of the article class.
Root notation. Use tsqrt (Just n) x for the nth root of x. When Nothing is supplied, the function will output a square root.
The proof environment. The first optional argument is used to put a custom title to the proof.
Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.